Rotating Cavity Liquid Detection via Magnetic Coupling
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Solution Overview
Problem
Existing electric machines face challenges in detecting liquid contaminants in their cavities, particularly in MW-range industrial applications, leading to undesirable outcomes such as bearing deterioration or pressure reversal, with high downtime and repair costs, and existing detection methods are hindered by the rotary nature of the parts and the gap between the stator and rotor.
Innovation Solution
A magnetic field-based system is employed to transmit power across the gap between the stator and rotor, using an interrogation circuit with a coil to detect changes in impedance due to liquid permittivity or resistivity, and a detection circuit to identify liquid contaminants, such as water infiltration in turbines, by monitoring changes in impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector is installed in the rotating rotor to detect liquid contaminants, then detection capability is improved, but the complexity of the rotating system increases and reliability decreases due to the harsh operating environment
Solution Approach 1:
Instead of placing the detector in the rotating rotor, the patent inverts the arrangement by placing the detector in the stationary stator. The interrogation circuit remains in the rotor while the detection circuit is in the stator, allowing detection without exposing sensitive components to the harsh rotating environment. This resolves the contradiction by achieving detection capability while maintaining reliability through proper component placement.
Solution Approach 2:
The patent uses magnetic coupling across the air gap as an intermediary mechanism to transmit both power and detection signals between the rotating rotor and stationary stator without direct physical connection. This allows the detector to remain in the reliable stationary position while still detecting contaminants in the rotating cavity, resolving the contradiction between detection capability and reliability.
2Ease of operation
If electrical contacts are placed in the rotating rotor for detection, then detection function is achieved, but the complexity of the rotating system increases due to additional wiring and power transmission requirements
Solution Approach 1:
The patent extracts the detection circuit from the rotating system and places it in the stationary stator, leaving only the simple interrogation circuit with electrical contacts in the rotor. This extraction reduces rotating system complexity while maintaining the detection function through magnetic coupling across the air gap.
Solution Approach 2:
The patent replaces complex mechanical wiring and sliding contacts for power transmission with electromagnetic induction through the air gap. The interrogation circuit uses magnetic coupling to transmit power and signals wirelessly to the stator, eliminating the need for complex mechanical connections in the rotating system.
3Measurement precision
If the spacing between electrical contacts is reduced to improve sensitivity, then detection sensitivity increases, but the risk of liquid infiltration between contacts increases
Solution Approach 1:
The patent uses the air gap itself as a protective barrier that can be easily maintained. The spacing between electrical contacts is designed to be sufficient to prevent liquid infiltration while still allowing effective magnetic coupling, trading a small amount of sensitivity for reliable operation without complex sealing mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Early detection of liquid contaminants, such as water in turbines, allows for timely maintenance, preventing oil leakage and reducing downtime and repair costs, while overcoming the challenges of powering detectors in rotating environments.
Implementation Method 1
a magnetic field source mounted to said stator and transmitting a magnetic field across a gap between said stator and said rotor
Implementation Method 2
an interrogation circuit mounted to said rotor and having a coil magnetically coupled to said magnetic field source across said gap via said magnetic field
Implementation Method 3
a detection circuit mounted to said stator, the detection circuit having a coil electromagnetically coupled to said magnetic field and a detector configured for detecting the influence of the interrogation circuit on the magnetic field
Data Source
AI summary
The apparatus can be used for detecting a liquid contaminant in a rotating cavity of an electric machine. The apparatus can have a magnetic field source mounted to a non-rotary base and transmitting a magnetic field across a gap between the base a housing of the cavity, an interrogation circuit having a coil magnetically coupled to the magnetic field source across the gap via the magnetic field, and a distal circuit portion having electrical contacts separated by a spacing fluidly communicating with the cavity; and a detection circuit mounted to the base and having a coil magnetically coupled to the magnetic field and a detector detecting a variation occurring in the detection circuit upon change of a permittivity of the liquid across the spacing, the variation being indicative of the liquid contaminant.